Vertical Gardens Basics

MANILA, Philippines - Vertical gardens are nothing new. We have seen it in nature: on cliffs and ravines, on epiphytic growths on big trees and even feral plants on cement walls. The hanging Gardens of Babylon may be considered vertical gardens.

The Japanese gardeners have done square blocks of mosses for Zen Garden walls. Filipino Gardeners have done vertical gardens when they dress up blank walls with epiphytes like orchids, ferns, Hoyas and Huperzias.

There are many types and ways of doing vertical gardens. Most gardeners with good understanding of plants can do it well.

Some critical factors that need to be considered in putting up a vertical garden are as follows:

Plant Choices

Plants are chosen based on the location and purpose of the project. Example: Plants destined for use in an air-conditioned space should be able to withstand dry air environments. Plants for use near air-ducts, aside from being able to withstand dry air should survive the strong wind velocities. For this purpose, the cacti and succulents will be your best bet for the project.

Open wall gardens with strong sun exposures may need full-sun landscaping plants while vertical gardens in between tall buildings should use indoor plants because of lower light intensities.

Within the same vertical garden even, the lower areas get more water than the top (water tends to settle in the lower section of the substrate), i.e. top areas get dry-tolerant plants while the lower areas may need wet-tolerant plants like Selaginellas, Tradescantias, Episcias and Begonias.

Color-based designs will require variegata, flava, reds, browns and purples. All-green designs need a variety of leaf sizes, leaf shapes, textures and hues to effect a strong visual impact.

Media

Choice of media or substrate is very critical for a successful vertical garden project. It is the media that will hold the water needed by the plants for survival and growth.

For modular systems, the usual media used are: peat moss, rockwool chips, coconut husk chunks, cocopeat, charcoal, pumice, vermiculite, happu, fermented tree bark, sphagmum moss, rubberized foam, floral foam, Styrofoam balls and peanuts, treefern roots and paslak (Asplenium or Platycerium roots).

The choice of substrate or media mix is dependent on the choice of plants. Big-rooted plants like Anthuriums, Philodendrons and epiphytic orchids need very chunky substrate while fine-rooted plants like Selaginella, Pilea, Hedera, etc. need finer, more absorbent media mix. There is not one singular mix that will satisfy all plants.

Watering, whether it is overhead, drip, spaghetti tube fed, turbo-emitted or hand-watered will depend on the media and plant used.

Substrates initially are wet to saturation before plants are installed. As the media dry up, a film of microorganisms develops. As the surface of the media materials dry up, the microbial film becomes hydrophobic, meaning water will bounce off the surface of the material instead of it being absorbed by the substrate. Water applied to the modules will channel its way down the box without wetting much the media. Plants will be deprived of the needed moisture and root tips will eventually dry up causing shedding of lower leaves. 

Maintenance of Vertical Gardens

Water management is the core of Vertical Garden Maintenance. Since media desiccation is the main problem, application of ethoxide surfactants (re-wetting agent) should be done at least monthly. Surfactants will help redistribute moisture within the module.

Drippings from the surfactant-treated media should collect in a system separate from live fishes. Surfactants will kill the fishes and other aquatic creatures.

Pests should be dealt with as early as they appear. Soap solution may be used to manage insect and mite populations. Fungal problems are caused by water in the wrong places at the wrong times. Generally water should go to the root zone not on the leaves.

Only healthy plants should be used in vertical garden set-ups. Chlorotic, nutrient deficient plants will stick out like sore thumb on the vertical gardens. 

Fertilizers with chelated trace elements should be applied regularly as foliar spray because most modules do not have nutrients in them. Calcium may be applied monthly as foliar spray or media drench as Calcium nitrate solution.

Plants may not grow at the same rate. Some varieties may grow faster than others and will need more frequent trimming to maintain the overall form of the vertical garden.

Planting Systems

Modular systems have been around for more than 3 decades. These are usually boxes either in plastic or welded wire casing lined with nonwoven polyester fibers or geotextiles and filled with media mix inside. Some modules may be stacked on each other with water line built into the design. Most may be hanged on the wall while others are free forms. 

The most common workable system for tropical conditions was developed in Thailand using Carpetbacking as substrate, mat-base and plant pockets. The system may be hanged on any wall. This maintenance-friendly design is easy to repair and plant re-placement is just a matter of pulling out damaged plant and sticking the new plant into the vacated pocket.

Whatever the design and system chosen for the vertical garden, it will ultimately be the gardener’s skill that will determine the success or failure of the vertical garden project.